Earthquake Resistant Design for Low Rise Open Ground Storey Famed Building

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1 IJSTE - International Journal of Science Technology & Engineering Volume 2 Issue 11 May 2016 ISSN (online): X Earthquake Resistant Design for Low Rise Open Ground Storey Famed Building Himanshu Mishra Department of Civil Engineering Madan Mohan Malaviya University of Technology, Gorakhpur. Abstract In frame building design we generally ignore the consideration of the stiffness by the infill walls and this stiffness plays an important role during the strong earthquake. In open ground storey building stiffness is absent at ground floor level due to which the failures occur at that level. The present study deals with the study of Linear Time History Analysis to analyze the behaviours of building. There are six different cases of ground motion (unidirectional and bidirectional) on which the performance of the buildings will be analyzed. It is found after analysis that when the stiffness consideration is provided in the building the time period tends to decreases as a result of which the base shear is increased. The behavioural change in open ground storey there are large variation in the ground storey level in terms of displacement as compare as the upper stories of the building. Keywords: Stiffness, Time history analysis, Time period base shear I. INTRODUCTION As the city is developing the people generally do not prefer the basement in the building for the parking due the fact that it is comparatively expensive. In that case the open ground storey is preferred than basements. The open ground storey building is also known as Soft Storey Building. In India commonly while design practices the strength and stiffness of infill walls are ignored. Hence column and beam of the building get heavily stressed and the forces become more which causes failure of the building. Infill walls add considerably to the rigidity and strength of the structures and their negligence will cause failure of buildings. In soft storey building we analysed that the basic failures of the building are snapping of lateral ties, buckling of longitudinal reinforcement bar, crushing of core concrete etc. In this study we select the two types of buildings: 1) Bare frame building (Building without Infill walls) 2) Open Ground Storey building( Building having infill walls except ground storey) These two buildings are modelled on the SAP2000 Software by using IS 1893:2002 and FEMA 356. I am using the method for analysis on building is Time History Analysis Method. Time history analysis method is considered as finest analysis of the building. In time history analysis the structural response is computed at a number of subsequent time instants. This model has been exposed to acceleration time histories to calculate the dynamic behaviour of a low rise building during earthquakes. There is a clear need to assess the design guidelines recommended by the IS code of 1893:2002 based on accurate analysis. In this study, time history analysis has two different approaches is used 1) Linear Direct Integration Time History Analysis 2) Linear Modal Time History Analysis Structural Modelling: An Open Ground Storey Framed Building is designed as per the Norms of the codal provisions. The building is designed for the fifth zone for which the study has been done. The building is symmetrical in plan and in elevation. The building is G+4 storey building of total height 14.9 m. Ground floor is 2.5 m and the rest floor is 3.1 m. The X-direction of the building having 15 m length and at the Y-direction 8 m length. The 150 mm is the thick of the floor at each level. The thickness of the wall is taken as 230 mm. The imposed load is considered as 2 KN/m 2 for each floor but in the roof it taken as 1 KN/m 2 for the residential building. The structural modal of building is symmetrical in dimension. The size of the column and beam is (300 mm * 450 mm). Both having same size but the reinforcement is varying. In the concrete section M20 Grade is used and for the steel section Fe415 is taken for all the frames models. Elastic Material Properties of material will take by the Indian Stranded IS 456:200. The framed building column ends are designing as isolated footing. The column end is modelled as fixed at the top of the isolated foundation. When the end of column are fixed the all the forces and moment are to be calculated. Ground motion and combination which is used in the time history methods are detailed in the table. Peak ground motion 0.31g and 0.21g is used in the study. There are two types of ground motion and six cases are formed by these ground motion. Table 1 Details of the Ground Motions Cases Case No. Case Name Direction of Propagation (Angle) Case g U1 X direction Case g U1 45 X-direction(45) Case g U g U2 Both direction All rights reserved by 110

2 II. METHODOLOGY Calculation of Time Period and Base Shear (IS 1893:2002): The calculation of design base shear (V ) as per IS 1893: 2002 with the fundamental period for the moment-resisting framed B buildings with or without brick infill panels as follows: V b=a hw where W =seismic weight of the building, Z = zone factor, I = importance factor, R = response reduction factor, S a /g = spectral acceleration coefficient For calculating the spectral acceleration coefficient we need to calculate the time period as follows Linear Time History Analysis: Time history analysis is a step-by-step analysis method. It is a dynamic response of the structure for a arbitrary loading that is varing with the time. The dynamic equation to be solved by time history analysis are given by Ku(t) + Cu (t) + Mu (t) = r(t) K = stiffness matrix C = damping matrix M = diagonal matrix u = displacement u. = velocity u.. = acceleration r = rapid loading. If load includes ground motion acceleration the displacent velocity and acceleration are relative to ground motion. The Time history case of any number can be defined. Each cases are differ in the applied load and the types of analysis will be performed. Moadal Time History analysis It is used for determining the vibration mode of a structure / building. The vibration modes are very much useful to know the behaviours of the structure / building. This is always linear. The load cases of modal are based on the stiffness of full unstressed. Direct Integration Time History Analysis Direct integration for the full equations of motion without using of modal superposition is available in SAP2000. Direct integration results are seem to be extremely sensitive to time-step size in that way it is not true for modal superposition. The modal superposition is usually more correct and efficient; direct-integration does offer the following advantages for linear problems: - Full damping that couples the modes can be considered - Impact and wave propagation problems that may excite a large number of modes might be more efficiently solved by direct integration. III. RESULT AND DISCUSSION On calculation of the base shear of the soft storey building are 714 KN/m 2 and 570 KN/m 2 on time period 0.42 and 0.69 respectively. This variation shows that when the building has provided with infill walls then the time period will decrease. Time History Method result and graph are given below. First here gives the result and graphs of Direct Integration Method All rights reserved by 111

3 a: X-direction displacement b: Y-direction displacement c: Maximum displacement of each story case 1 Fig. 1: Displacement of building without and with infill in Case 1 a: X-direction displacement b: Y-direction displacement c: Maximum displacement of each story case 2 Fig. 2: Displacement of building without and with infill in Case 2 All rights reserved by 112

Table 1 Details of Shear force and Bending Moment of Cases by Linear Direct Integration Without infill With Infill Case 1 Case 2 Case 5 Case 1 Case 2 Case 5 Max.

7: Inter-Storey Drift for Infill and Without Infill of Case 1 Fig. 4.

4 Table 1 Details of Shear force and Bending Moment of Cases by Linear Direct Integration Without infill With Infill Case 1 Case 2 Case 5 Case 1 Case 2 Case 5 Max. Shear Force (KN) Max. Bending Moment (KN-m) Maximum Displacement (mm) Fig. 4.7: Inter-Storey Drift for Infill and Without Infill of Case 1 Fig. 4.8: Inter-Storey Drift for Infill and Without Infill of Case Fig. 4.11: Inter-Storey Drift for Infill and Without Infill of Case 5 Second Method used for the study is Modal Time History Analysis and result and graphs are given below: All rights reserved by 113

5 a: X-direction displacement b: Y-direction displacement c: Maximum displacement of each story case 1 Fig. 4.13: Displacement of building without and with infill in Case 1 a: X-direction displacement b: Y-direction displacement c: Maximum displacement of each story case 2 Fig. 4.14: Displacement of building without and with infill in Case 2 All rights reserved by 114

6 a :- X-direction displacement b :- Y-direction displacement c: Maximum displacement of each story case 5 Fig. 4.17: Displacement of building without and with infill in Case 5 Table 2 Details of Shear force and Bending Moment of Cases by Modal Analysis Without infill With Infill Case 1 Case 2 Case 5 Case 1 Case 2 Case 5 Max. Shear Force (KN) Max. Bending Moment (KN-m) Maximum Displacement (mm) Fig. 4.13: Inter-Storey Drift for Infill and Without Infill of Case 1 All rights reserved by 115

7 Fig. 4.14: Inter-Storey Drift for Infill and Without Infill of Case 2 Fig. 4.17: Inter-Storey Drift for Infill and Without Infill of Case5 IV. CONCLUSIONS 1) When the stiffness is provided in the building then the time period of the building decreases which makes the open ground storey building stiffer than the bare frame building. But at ground floor level of open ground storey buildings no stiffness is provided, which causes the large deformation, during strong ground motion. 2) From the time history analysis it is found that the displacement of the bare frame building is larger compared to the open ground storey building. But in open ground storey building the displacement is maximum at first storey and the upper stories are behaves like a lumped mass because of stiffness present. 3) For the different cases of ground motion as stated in table above, the shear forces and the bending moments in the base of the building is maximum in soft storey building as compared to the bare framed building. 4) From compression in term of inter storey drift it is found that the inter storey drift is maximum in bare framed building (2nd storey). But in case of open ground storey building the inter storey drift is maximum at ground floor level. 5) In comparison of graphs of X-direction and Y-direction for top storey of all cases it is found that the displacement of soft storey building is maximum in Y-direction as compare to the X-direction. 6) In unidirectional ground motions cases defined in table above, the behaviour of the building is found that the displacement is maximum where the ground motion is propagated of ground motion and displacement is negligible in orthogonal direction. But in bidirectional ground motion cases displacement occurs at both direction which causes the building having the maximum shear force and bending moment. 7) The case where ground motion is in 45 0 angles it is found that the building is displaced in both the direction (X and Y- direction). REFERENCES [1] IS 1893 Part 1 (2002) Indian Standard Criteria for Earthquake Resistant Design of Structures, Bureau of Indian Standards, New Delhi. [2] SAP 2000 (Version 11.0). (2007) Integrated Software for Structural Analysis and Design. Computers & Structures, Inc., Berkeley, California. [3] Holmes, M. (1961) Steel frames with brick and concrete infilling. Proceedings of Institution of Civil Engineers [4] Mallick D.V. and Severn R.T., (1967), The Behaviour of Infilled Frames under Static Loading, The Institution of Civil Engineers, Proceedings [5] Rao, S. P.; H. Achyutha and R. Jagdish (1982) Infilled frames with opening strengthened by lintel beam. Proceedings of the 6 th International Brick Masonry Conference. Rome [6] Karisiddappa, (1986) Effect of position of openings on the behaviour of infilled frames. M.Tech Thesis. Indian Institute of Technology Madras, Chennai. All rights reserved by 116

8 [7] Arlekar, J.N.; S. K. Jain and C.V.R Murty (1997) Seismic response of RC frame buildings with soft first storeys. Proceedings of CBRI golden jubilee conference on natural hazards in urban habitat. New Delhi [8] Riddington, J. R. and S. B. Smith (1977) Analysis of infilled frames subject to racking with design recommendations. The Structural Engineer [9] Scarlet, A. (1997) Design of Soft Stories A simplified energy approach. Earthquake Spectra [10] Das, S. and J. M. Nau (2003) Seismic design aspects of vertically irregular reinforced concrete buildings. Earthquake Spectra [11] A. Asokan, (2006) Modelling of Masonry Infill Walls for Nonlinear Static Analysis of Buildings under Seismic Loads. M. S. Thesis, Indian Institute of Technology Madras, Chennai. [12] Hashmi, A. K. and A. Madan (2008) Damage forecast for masonry infilled reinforced concrete framed buildings subjected to earthquakes in India, Current Science [13] Jinyawala Mohammad (2014) ANALYSIS OF RC FRAME WITH AND WITHOUT MASONRY INFILL WALL WITH DIFFERENT STIFFNESS WITH OUTER CENTRAL OPENING M. S. University of Baroda, Vadodara, India [14] S. B. Smith and C. Carter, (1969) A Method of Analysis for Infilled Frames. Proceedings of Institution of Civil Engineers [15] Ramesh, P. (2003) Retrofitting of masonry infill walls to resist earthquake loads. M.Tech Thesis. Indian Institute of Technology Madras. Chennai. [16] Govindan, P. and D. Vivekanandan(1990 Effect of Opening in Brick Infilled Square Panel, Indian Concrete Journal [17] Mainstone, R. J. (1971) On the stiffness and strength of infilled frames. Proceedings of Institution of Civil Engineers. Supplementary [18] Al-Chaar, G., M. Issa and S. Sweeney (2002) Behaviour of masonry infilled non-ductile RC frames. Journal of Structural Engineering. American society of Civil Engineers. 128(8) All rights reserved by 117

SEISMIC RESPONSE OF A MID RISE RCC BUILDING WITH SOFT STOREY AT GROUND FLOOR

SEISMIC RESPONSE OF A MID RISE RCC BUILDING WITH SOFT STOREY AT GROUND FLOOR 1 DHARMESH VIJAYWARGIYA, 2 Dr. ABHAY SHARMA, 3 Dr. VIVEK GARG 1 Post Graduate Student, Civil Engineering Department, MANIT,